The present invention relates to rubber compositions particularly suited for use in the sidewall of a pneumatic tire. The sidewall of a pneumatic tire is subjected to severe weathering and dynamic flexing. Typically, such sidewall compositions contain various antiozonants/antioxidants (hereinafter referred to as antidegradants). Surprisingly, it has been discovered that the properties of conventional antidegradants in sidewall compositions can be enhanced when such sidewall compositions contain a silica filler having a defined pH.